1. Field of the Invention
The present invention relates to a digital mobile communication system, and more specifically to direct communication between mobile terminals without intervention of a base station.
2. Prior Art
Interterminal direct communication is one of most useful features of a digital cordless telephone which is called PHS (Personal Handy phone System). In the interterminal direct communication mode, it is required that connection control and communication between mobile terminals are performed on a certain time slot of a communication channel (RCR STD-28: Research & Development Center for Radio Systems Standards 28). Therefore, the mobile terminals need to repeat a scan of all the communication channels for detection of an unique word (or a synchronization word) to be synchronized with each other. Furthermore, a calling mobile terminal finds an idle channel, and then transmits a connection control signal continuously for a predetermined period of time, while waiting for a response signal through the same channel. After the calling party and the called party are synchronized, the well-known connection sequence proceeds.
However, in order to take synchronization with each other, the above-mentioned conventional PHS terminal repeats a scan of all the channels and , when it originates a call, the control signal is transmitted continuously. Since such an operation causes power consumption to increase, the battery incorporated in the terminal runs down in a short time.